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Don't dorp those apples ​

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Answered by sairishipopuri2010
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Answer:

previous classes; however, you will be

studying about them in detail in Unit 2.

Sodium, copper, silver, hydrogen, oxygen,

etc., are some examples of elements. Their

all atoms are of one type. However, the

atoms of different elements are different in

nature. Some elements, such as sodium or

copper, contain atoms as their constituent

particles, whereas, in some others, the

constituent particles are molecules which

are formed by two or more atoms. For

example, hydrogen, nitrogen and oxygen

gases consist of molecules, in which two

atoms combine to give their respective

molecules. This is illustrated in Fig. 1.3.

carbon atom. Thus, the atoms of different

elements are present in a compound in a fixed

and definite ratio and this ratio is characteristic

of a particular compound. Also, the properties

of a compound are different from those of its

constituent elements. For example, hydrogen

and oxygen are gases, whereas, the compound

formed by their combination i.e., water is a

liquid. It is interesting to note that hydrogen

burns with a pop sound and oxygen is a

supporter of combustion, but water is used

as a fire extinguisher.

1.3 PROPERTIES OF MATTER AND

THEIR MEASUREMENT

1.3.1 Physical and chemical properties

Every substance has unique or characteristic

properties. These properties can be classified

into two categories — physical properties,

such as colour, odour, melting point, boiling

point, density, etc., and chemical properties,

like composition, combustibility, ractivity with

acids and bases, etc.

Physical properties can be measured or

observed without changing the identity or the

composition of the substance. The measurement

or observation of chemical properties requires

a chemical change to occur. Measurement of

physical properties does not require occurance

of a chemical change. The examples of chemical

properties are characteristic reactions of different

substances; these include acidity or basicity,

combustibility, etc. Chemists describe, interpret

and predict the behaviour of substances on the

basis of knowledge of their physical and chemical

properties, which are determined by careful

measurement and experimentation. In the

When two or more atoms of different

elements combine together in a definite ratio,

the molecule of a compound is obtained.

Moreover, the constituents of a compound

cannot be separated into simpler

substances by physical methods. They can

be separated by chemical methods.

Examples of some compounds are water,

ammonia, carbon dioxide, sugar, etc. The

molecules of water and carbon dioxide are

represented in Fig. 1.4.

Note that a water molecule comprises two

hydrogen atoms and one oxygen atom.

Similarly, a molecule of carbon dioxide

contains two oxygen atoms comb

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